Near infrared control coating, articles formed therefrom, and methods of making the same

ABSTRACT

A coating composition for application over a retroreflective substrate, a retroreflective article comprising a coating formed from the coating composition, and a method of production thereof are provided. The coating composition comprises a pigment suitable to absorb and/or scatter electromagnetic radiation in a wavelength range of 800 nm to 2000 nm. The coating comprises a ratio of reduction in electromagnetic radiation retroreflectance at a wavelength of 905 nm and/or 1550 nm to reduction in electromagnetic radiation retroreflectance averaged over a wavelength range of 400 nm to 700 nm of at least 2:1.

FIELD

A coating composition for application over a retroreflective substrate,a retroreflective article comprising a coating formed from the coatingcomposition, and a method of production thereof are provided. Thepresent disclosure can relate to reduction in near infrared (NIR)transmittance by the coating.

BACKGROUND

Autonomous vehicles can use various sensor systems such as, cameras,radar, and LIDAR (Light Imaging, Detection, and Ranging), to detect andlocate obstacles in order to safely navigate through an environment.Typically, a LIDAR system includes a NIR source to emit NIRelectromagnetic radiation and a NIR detector to detect NIRelectromagnetic radiation reflected by the obstacle. A NIRelectromagnetic radiation source can comprise, for example, a lightemitting diode, a laser diode, or any light source that can be capableof emitting NIR electromagnetic radiation. A NIR detector may be asemiconductor detector that can be capable of sensing NIRelectromagnetic radiation, such as, a photodiode, a silicon-basedcharged-coupled device, an indium gallium arsenide detector, a leadsulfide detector, and a lead selenide detector. Some obstacles maypresent detection challenges for some LIDAR systems.

SUMMARY

The present disclosure provides a coating composition for applicationover a retroreflective substrate. The coating can comprise a resin and apigment. The pigment can be suitable to absorb and/or scatterelectromagnetic radiation in a wavelength range of 800 nm to 2000 nm. Acoating formed from the coating composition can comprise a ratio ofreduction in electromagnetic radiation retroreflectance at a wavelengthof 905 nm and/or 1550 nm to reduction in electromagnetic radiationretroreflectance averaged over a wavelength range of 400 nm to 700 nm ofat least 2:1.

The present disclosure also provides a method for producing aretroreflective article with reduced electromagnetic radiationretroreflection at a wavelength of 905 nm and/or 1550 nm. A coatingcomposition may be deposited over a retroreflective substrate to form acoating. The coating composition can comprise a resin and a pigment. Thepigment can be suitable to absorb and/or scatter electromagneticradiation in a wavelength range of 800 nm to 2000 nm. The coating cancomprise a ratio of reduction in electromagnetic radiationretroreflectance at a wavelength of 905 nm and/or 1550 nm to reductionin electromagnetic radiation retroreflectance averaged over a wavelengthrange of 400 nm to 700 nm of at least 2:1.

The present disclosure also provides a retroreflective article. Thearticle can comprise a retroreflective substrate and a coating disposedover the retroreflective substrate. The coating can comprise a resin anda pigment. The pigment can be suitable to absorb and/or scatterelectromagnetic radiation in a wavelength range of 800 nm to 2000 nm.The coating can comprise a ratio of reduction in electromagneticradiation retroreflectance at a wavelength of 905 nm and/or 1550 nm toreduction in electromagnetic radiation retroreflectance averaged over awavelength range of 400 nm to 700 nm of at least 2:1.

It is understood that the inventions described in this specification arenot limited to the examples summarized in this Summary. Various otheraspects are described and exemplified herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the examples, and the manner of attainingthem, will become more apparent, and the examples will be betterunderstood by reference to the following description of examples takenin conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram illustrating a retroreflective articlewith a coating according to the present disclosure;

FIG. 2 is a graph depicting transmission spectra for coatings ATO-1 andATO-2 according to the present disclosure;

FIG. 3 is a graph depicting extinction spectra for coatings ATO-1 andATO-2 according to the present disclosure;

FIG. 4 is a graph depicting transmission spectra for coatings LaB₆-1 andLaB₆-2 according to the present disclosure;

FIG. 5 is a graph depicting extinction spectra for coatings LaB₆-1 andLaB₆-2 according to the present disclosure;

FIG. 6 is a graph depicting a transmission spectrum for coating Au-1according to the present disclosure; and

FIG. 7 is a graph illustrating reflectivity spectra for coating LaB₆-2deposited on a white colored aluminum panel according to the presentdisclosure.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate certain examples, in one form, and such exemplifications arenot to be construed as limiting the scope of the examples in any manner.

DETAILED DESCRIPTION

Certain exemplary examples of the present disclosure will now bedescribed to provide an overall understanding of the principles of thecomposition, function, manufacture, and use of the compositions andmethods disclosed herein. One or more examples are illustrated in theaccompanying drawings. Those of ordinary skill in the art willunderstand that the compositions, articles, and methods specificallydescribed herein and illustrated in the accompanying drawings arenon-limiting exemplary examples and that the scope of the variousexamples of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryexample may be combined with the features of other examples. Suchmodifications and variations are intended to be included within thescope of the present invention.

Reference throughout the specification to “various examples,” “someexamples,” “one example,” “an example,” or the like, means that aparticular feature, structure, or characteristic described in connectionwith the example is included in at least one example. Thus, appearancesof the phrases “in various examples,” “in some examples,” “in oneexample,” “in an example,” or the like, in places throughout thespecification are not necessarily all referring to the same example.Furthermore, the particular features, structures, or characteristics maybe combined in any suitable manner in one or more examples. Thus, theparticular features, structures, or characteristics illustrated ordescribed in connection with one example may be combined, in whole or inpart, with the features, structures, or characteristics of one or moreother examples without limitation. Such modifications and variations areintended to be included within the scope of the present examples.

As used in this specification, particularly in connection with coatinglayers or films, the terms “on,” “onto,” “over,” and variants thereof(e.g., “applied over,” “formed over,” “deposited over,” “provided over,”“located over,” and the like) mean applied, formed, deposited, provided,or otherwise located over a surface of a substrate but not necessarilyin contact with the surface of the substrate. For example, a coatinglayer “applied over” a substrate does not preclude the presence of oneor more other coating layers of the same or different compositionlocated between the applied coating layer and the substrate. Likewise, asecond coating layer “applied over” a first coating layer does notpreclude the presence of one or more other coating layers of the same ordifferent composition located between the applied second coating layerand the applied first coating layer.

As used in this specification, the terms “polymer” and “polymeric” meansprepolymers, oligomers, and both homopolymers and copolymers. As used inthis specification, “prepolymer” means a polymer precursor capable offurther reactions or polymerization by one or more reactive groups toform a higher molecular mass or cross-linked state.

As used in this specification, the terms “cure” and “curing” refer tothe chemical crosslinking of components in a coating composition appliedas a coating layer over a substrate. Accordingly, the terms “cure” and“curing” do not encompass solely physical drying of coating compositionsthrough solvent or carrier evaporation. In this regard, the term“cured,” as used in this specification, refers to the condition of acoating layer in which a component of the coating composition formingthe layer has chemically reacted to form new covalent bonds in thecoating layer (e.g., new covalent bonds formed between a binder resinand a curing agent).

As used in this specification, the term “formed” refers to the creationof an object from a composition by a suitable process, such as, curing.For example, a coating formed from a curable coating composition refersto the creation of a single or multiple layered coating or coatedarticle from the curable coating composition by curing the coatingcomposition under suitable process conditions.

Retroreflective substrates have been used on various articles, such as,for example, a tape, a sign, a vehicle, a marker, and clothing, in orderto increase their visibility upon illumination at night. The increasedvisibility can enhance the ability of a driver to see the sign,including the retroreflective substrate (e.g., a stop sign, a yieldsign, a one-way sign), or a person wearing clothing, including theretroreflective substrate. The increased visibility can enable thedriver to safely observe the article and navigate around the article orperson.

A retroreflective substrate operates by receiving electromagneticradiation from an electromagnetic radiation source and reflecting thereceived electromagnetic radiation back to the electromagnetic source inthe anti-parallel direction it was received. For example,electromagnetic radiation received by a retroreflective substratetraveling in a source vector can be reflected back along a return vectorsubstantially parallel to the source vector but in the oppositedirection of the source vector.

As used herein, the term “retroreflectance” means the ability of anarticle to reflect electromagnetic radiation in a return vector that issubstantially parallel but opposite to a source vector and/or theability of a coating to permit the reflectance of electromagneticradiation by the article in a return vector that is substantiallyparallel but opposite to a source vector. As used herein, the term“reflectance” means the returning or throwing back of electromagneticradiation by a surface upon which the electromagnetic radiation isincident. As used herein, the term “extinction” means the absorbingand/or scattering of electromagnetic radiation.

As used herein, the terms “near infrared range” or “NIR” refer to thenear infrared range of the electromagnetic spectrum. For example, theNIR range may have a wavelength range of 800 nm to 2000 nm, such as, 800nm to 1600 nm. The NIR range may include a wavelength of 905 nm and/or1550 nm. As used herein, the term “visible” refers to the visible rangeof the electromagnetic spectrum. For example, the visible range may be awavelength range of 400 nm to 700 nm.

As used herein, the term “NIR retroreflectance” means the ability of anarticle to retroreflect electromagnetic radiation in the NIR range ofthe electromagnetic spectrum and/or the ability of a coating to permitthe retroreflectance of the article in the NIR range of theelectromagnetic spectrum. As used herein, the term “visibleretroreflectance” means the ability of an article to retroreflectelectromagnetic radiation in the visible range of the electromagneticspectrum and/or the ability of a coating to permit the retroreflectanceof the article in the visible range of the electromagnetic spectrum. Asused herein, the term “NIR extinction” means the ability of a coating toabsorb and/or scatter electromagnetic radiation in the NIR range of theelectromagnetic spectrum. As used herein, the term “visible extinction”means the ability of a coating to absorb and/or scatter electromagneticradiation in the visible range of the electromagnetic spectrum.

It can be a challenge for LIDAR systems to properly detect the size andposition of a retroreflective substrate because the retroreflectivesubstrate may reflect more NIR electromagnetic radiation back to theLIDAR system than a similarly positioned and sized non-retroreflectivesubstrate. The increased reflectance can result in system saturationthat may lead to an improper calculation by the LIDAR system. As aresult, the article that employs the retroreflective substrate mayappear to the LIDAR system to be larger than a similarly positioned andsized non-retroreflective substrate. The improper calculation can leadto inaccurate mapping of an environment by the LIDAR system and, thus,inaccurate navigation by an autonomous vehicle employing the LIDARsystem.

Provided herein are retroreflective substrates, coatings for applicationover a retroreflective substrate, retroreflective articles comprisingthe coating, and methods of production thereof. The coatings of thepresent disclosure can reduce the NIR retroreflectance of theretroreflective substrate and/or the NIR extinction of the coating whilemaintaining a sufficient level of visible retroreflectance and/orvisible extinction of the coating. The coatings can also enableautonomous vehicles to more accurately detect and calculate the sizeand/or position of the retroreflective substrate while still providingsufficient visible retroreflectance and/or extinction of the coating andminimizing a visible color change in the underlying substrate.

As illustrated in FIG. 1, a retroreflective article 100 comprising aretroreflective substrate 102 and a coating 104 disposed on theretroreflective substrate 102 is provided. The coating 104 can besuitable to scatter and/or absorb electromagnetic radiation in the NIRrange. The coating 104 can reduce NIR retroreflectance of theretroreflective substrate 102. The article can be, for example, at leastone of a tape, a sign, a vehicle, a marker, clothing, and any obstaclethat may be located in a path of a moving vehicle. A marker can compriseat least one of a barrier, a barricade, a speed bump, a traffic cone, aroad surface, and the like. A vehicle can comprise any type of movingvehicle, such as, at least one of an automobile, a bicycle, a truck, abus, an airplane, a boat, a drone, a submarine, and the like.

The retroreflective substrate 102 can comprise, for example, metal,plastic, ceramic, fabric, wood, cement, asphalt, glass, stone, andcombinations thereof. The metal can comprise tin, tin alloy, aluminum,aluminum alloy, iron, and iron alloy, and combinations thereof. Theplastic can comprise a polymeric material, such as, polyester,polyolefin, polyamide, cellulosic, polystyrene, polyacrylic,poly(ethylene naphthalate), polypropylene, polyethylene, nylon, ethylenevinyl alcohol, polylactic acid, poly(ethyleneterephthalate),polycarbonate, polycarbonate acrylobutadiene styrene, polyamide, andcombinations thereof.

The retroreflective substrate 102 can be at least partially coated witha coating composition of the present disclosure to form coating 104.Coating compositions of the present disclosure can be formulated as asolvent-based composition, a water-based composition, or a 100% solidcomposition that does not comprise a volatile solvent or aqueouscarrier. The coating compositions of the present disclosure can be aliquid at a temperature of −10° C. or greater, such as, 0° C. orgreater, 10° C. or greater, 30° C. or greater, 40° C. or greater, or 50°C. or greater, can be a liquid at a temperature of 60° C. or lower, suchas, 50° C. or lower, 40° C. or lower, 30° C. or lower, 10° C. or lower,or 0° C. or lower, and can be a liquid at a temperature in a range of−10° C. to 60° C., such as, −10° C. to 50° C., −10° C. to 40° C., −10°C. to 30° C., or 0° C. to 40° C. For example, the coating compositionsof the present disclosure can be a liquid at room temperature.

The coating compositions of the present disclosure can comprise a resinsuch as, a film-forming resin. The film-forming resin can include aresin that can form a self-supporting continuous film on surface of asubstrate (e.g., retroreflective substrate 102) upon removal of anydiluents or carriers present with the film-forming resin or upon curingat ambient or elevated temperature. A film-forming resin can comprise,for example, at least one of an automotive original equipmentmanufacturer coating composition, an automotive refinish coatingcomposition, an industrial coating composition, an architectural coatingcomposition, a coil coating composition, a packaging coatingcomposition, a marine coating composition, and an aerospace coatingcomposition, and the like.

The film-forming resin can comprise at least one of a thermosettingfilm-forming resin and a thermoplastic film-forming resin. As usedherein, the term “thermosetting” refers to resins that “set”irreversibly upon curing or crosslinking, where the polymer chains ofthe polymeric components are joined together by covalent bonds, which isoften induced, for example, by heat or radiation. Curing or acrosslinking reaction can be carried out under ambient conditions. Oncecured or crosslinked, a thermosetting film-forming resin may not meltupon the application of heat and can be insoluble in conventionalsolvents. As used herein, the term “thermoplastic” refers to resins thatinclude polymeric components that are not joined by covalent bonds andthereby can undergo liquid flow upon heating and are soluble inconventional solvents.

Thermosetting coating compositions may include a crosslinking agent thatmay be selected from, for example, aminoplasts, polyisocyanatesincluding blocked isocyanates, polyepoxides, beta-hydroxyalkylamides,polyacids, anhydrides, organometallic acid-functional materials,polyamines, polyamides, and mixtures of any of the foregoing.

A film-forming resin may have functional groups that are reactive withthe crosslinking agent. The film-forming resin in the coatingcompositions described herein may be selected from any of a variety ofpolymers well-known in the art. The film-forming resin may be selectedfrom, for example, acrylic polymers, polyester polymers, polyurethanepolymers, polyamide polymers, polyether polymers, polysiloxane polymers,copolymers thereof, and mixtures thereof. Generally, these polymers maybe any polymers of these types made by any method known to those skilledin the art. The functional groups on the film-forming resin may beselected from any of a variety of reactive functional groups, including,for example, carboxylic acid groups, amine groups, epoxide groups,hydroxyl groups, thiol groups, carbamate groups, amide groups, ureagroups, isocyanate groups (including blocked isocyanate groups),mercaptan groups, and combinations thereof.

The coating compositions of the present disclosure can comprise apigment suitable to reduce NIR transmittance and/or increase NIRextinction of the coating 104 formed therefrom and/or reduce NIRretroreflectance of the article 100. As used herein, the term “pigment”refers to inorganic or organic materials which are practically insolublein the medium in which they are incorporated. The pigment can comprisevarious compounds that can absorb and/or scatter NIR electromagneticradiation and the pigment can minimally, if at all, absorb and/orscatter visible electromagnetic radiation. The pigment can absorb NIRelectromagnetic radiation and minimally, if at all, scatter NIRelectromagnetic radiation. The pigment can scatter NIR electromagneticradiation and minimally, if at all, absorb NIR electromagneticradiation. The pigment can both scatter NIR electromagnetic radiationand absorb NIR electromagnetic radiation. The pigment can comprise, forexample, at least one of zinc oxide, alumina, antimony tin oxide,tungsten oxide (reduced or unreduced), gold nanoparticles, silvernanoparticles, copper nanoparticles, lanthanum hexaboride, dicopperhydroxide phosphate, and a phthalocyanine. For example, the pigment cancomprise or consist essentially of lanthanum hexaboride. Thenanoparticles can be spherical, rod-shaped, and/or tube-shaped. Thepreference of the pigment to absorb and/or scatter NIR electromagneticradiation can enable the coating composition and coating 104 formedtherefrom to reduce NIR transmittance while maintaining sufficientvisible transmittance.

The average particle size of the pigment can affect the NIR extinctionof the coating 104, the visible extinction of the coating 104, the NIRretroreflectance of the article 100, the visible retroreflectance of thearticle 100, and/or the observable color of the retroreflectivesubstrate 102. The average particle size of the pigment can be 1 nm orgreater such as, 10 nm or greater, 50 nm or greater, 100 nm or greater,200 nm or greater, 500 nm or greater, or 1000 nm or greater. The averageparticle size of the pigment can be 5000 nm or lower, such as, 1000 nmor lower, 500 nm or lower, 200 nm lower, 100 nm or lower, 50 nm orlower, or 10 nm or lower. The average particle size of the pigment canbe in a range of 1 nm to 5000 nm, such as, 1 nm to 1000 nm, 1 nm to 500nm, 10 nm to 500 nm, 10 nm to 150 nm, or 10 nm to 100 nm. Decreasing theaverage particle size of the pigment can increase a ratio of reductionin NIR transmittance to reduction in visible transmittance by thepigment.

As used herein, “average particle size” refers to the z-average sizemeasured using dynamic light scattering which is the intensity-weightedharmonic mean particle diameter. Average particle size according to thepresent disclosure can be measured according to ASTM E2490.

In order to make the coating composition, a pigment compositioncomprising the pigment can be combined with the film-forming resin. Thepigment composition can be formed by at least one of grinding andmilling a pigment source material in order to reduce the particle sizeof the pigment. For example, the average particle size of the pigmentcan be reduced to 5000 nm or lower, such as, a reduction to 1000 nm orlower, a reduction to 500 nm or lower, a reduction to 200 nm or lower, areduction to 100 nm or lower, or a reduction to 50 nm or lower. Forexample, the average particle size can be reduced to a range of 10 nm to5000 nm, such as, 10 nm to 1000 nm, 10 nm to 500 nm, 10 nm to 200 nm, 10nm to 100 nm, or 100 nm to 500 nm.

The pigment composition and film-forming resin can be mixed tohomogenize the components and form the coating composition. The coatingcomposition can be stored before use. The coating composition can becurable.

The coating compositions of the present disclosure can be formulatedwith a liquid viscosity suitable for atomization and droplet formationunder the high shear conditions associated with single or multiplecomponent airless spray application techniques at a temperature −10° C.or greater such as, a temperature of 0° C. or greater, a temperature of10° C. or greater, a temperature of 30° C. or greater, a temperature of40° C. or greater, or a temperature of 50° C. or greater. Thecompositions can be formulated with a liquid viscosity suitable foratomization and droplet formation under the high shear conditionsassociated with single or multiple component airless spray applicationtechniques at a temperature of 60° C. or lower such as, 50° C. or lower,40° C. or lower, 30° C. or lower, 10° C. or lower, or 0° C. or lower.Compositions of the present disclosure can be formulated with a liquidviscosity suitable for atomization and droplet formation under the highshear conditions associated with single or multiple component airlessspray application techniques in a temperature range of −10° C. to 60° C.such as, −10° C. to 50° C., −10° C. to 40° C., −10° C. to 30° C., or 10°C. to 40° C.

The coating compositions of the present disclosure can be deposited overthe retroreflective substrate 102 either in situ, after the article 100is already on location, or as part of the manufacturing process of thearticle 100. For example, compositions of the present disclosure can beapplied as an application over 5% or greater of an exterior surface areaof the retroreflective substrate 102, such as, 10% or greater, 20% orgreater, 50% or greater, 70% or greater, 90% or greater, or 99% orgreater, of an exterior surface area of the retroreflective substrate102. For example, the coating compositions can cover 100% or less of anexterior surface area of the retroreflective substrate 102, such as, 99%or less, 90% or less, 70% or less, 50% or less, 20% or less, or 10% orless, of an exterior surface area of the retroreflective substrate 102.For example, the coating compositions can cover 5% to 100% of anexterior surface area of the retroreflective substrate 102, such as, 5%to 99%, 5% to 90%, 5% to 70%, or 50% to 100%, of an exterior surfacearea of the retroreflective substrate 102.

By way of example, if the article 100 is a street sign, the coatingcomposition of the present disclosure may be applied on-site and form acoating over an existing and already installed street sign. Where thearticle 100 is a newly manufactured street sign, the coating compositionof the present disclosure may be applied as part of the manufacturingprocess of the street sign prior to on-site installation of the sign.Where the article 100 is newly manufactured clothing, the coatingcomposition of the present disclosure may be applied as part of themanufacturing process of the clothing. The coating composition of thepresent disclosure may be manufactured into a preformed film andthereafter applied to the article 100.

The coating composition can be deposited by at least one of spraycoating, spin coating, dip coating, roll coating, flow coating, and filmcoating. After deposition of the coating composition to theretroreflective substrate 102, the coating composition may be allowed tocoalesce to form a substantially continuous film on the retroreflectivesubstrate 102 and the coating composition can be cured to form thecoating 104. The coating composition can be cured at a temperature of−10° C. or greater such as, 0° C. or greater, 10° C. or greater, 20° C.or greater, 60° C. or greater, 100° C. or greater, 140° C. or greater,or 160° C. or greater. The coating composition can be cured at atemperature of 175° C. or lower such as, 160° C. or lower, 140° C. orlower, 100° C. or lower, 60° C. or lower, 20° C. or lower, 10° C. orlower, or 0° C. or lower. The coating composition can be cured at atemperature in a range of −10° C. to 175° C. such as, −10° C. to 160°C., 0° C. to 175° C., 10° C. to 175° C., 20° C. to 175° C., 60° C. to175° C., 10° C. to 100° C., 20° C. to 60° C., or 60° C. to 140° C. Thecuring can comprise a thermal bake in an oven.

The dry film thickness of the coating 104 can be 0.2 μm or greater, suchas, 0.25 μm or greater, 2 μm or greater, 10 μm or greater, 23 μm orgreater, 50 μm or greater, or 130 μm or greater. The dry film thicknessof the coating 104 can be 500 μm or less, such as, 130 μm or less, 50 μmor less, 23 μm or less, 10 μm or less, 2 μm or less, or 0.25 μm or less.The dry film thickness of the coating 104 can be in a range of 0.2 μm to500 μm, such as, 0.25 μm to 130 μm, 2 μm to 50 μm, or 10 μm to 23 μm.The dry film thickness of the coating 104 can affect the absorptionand/or scattering of NIR electromagnetic radiation by the coating 104.

The coating 104 may be a single layer or a multilayer coating system,such as a coating system including at least two coating layers, a firstcoating layer and a second coating layer underneath at least a portionof the first coating layer. The retroreflective article 100 can compriseadditional layers, such as, a clear coat, a primer, and combinationsthereof. Compositions of the present disclosure can be depositeddirectly on a surface of the retroreflective substrate 102 or over aprimer or other underlying layer.

The coating 104 can be substantially clear. As used herein, the term“substantially clear” refers to a coating that has a minimal, if any,scattering or diffuse reflection of visible electromagnetic radiation.The coating 104 can be colorless. The coating 104 may include acolorant; however, in such cases, the colorant is not present in anamount sufficient to render the coating 104 opaque.

As stated herein, the coating 104 can be suitable to reduce NIRretroreflectance of the retroreflective substrate 102. For example, asource 114 can comprise a NIR electromagnetic radiation source 114 a andemit NIR electromagnetic radiation 106, which can be absorbed by thecoating 104, can be scattered as diffuse NIR electromagnetic radiation108 b upon traversing the coating 104, and/or can reach theretroreflective substrate 102. The NIR electromagnetic radiation 106that reaches the retroreflective substrate 102 can be reflected backthrough the coating 104 to the source 114 as returned NIRelectromagnetic radiation 108 a. The returned NIR electromagneticradiation 108 a can be traveling in a first vector substantiallyparallel to a second vector that NIR electromagnetic radiation 106 istraveling. The first vector can be in a direction opposite of adirection of the second vector. The diffuse NIR electromagneticradiation 108 b may not return to source 114.

The source 114 can comprise a NIR detector 114 b. The returned NIRelectromagnetic radiation 108 a can be sensed by NIR detector 114 b. Dueto the absorption and/or scattering of the NIR electromagnetic radiation106 by the coating 104, the returned NIR electromagnetic radiation 108 ahas a reduced magnitude compared to a magnitude of the NIRelectromagnetic radiation 106. The reduced magnitude can prevent the NIRdetector 114 b from becoming saturated with NIR electromagneticradiation.

As illustrated in FIG. 1, the source 114 can comprise a visibleelectromagnetic radiation source 114 c and emit visible electromagneticradiation 110, which may be substantially unaffected by the coating 104.The visible electromagnetic radiation 110 can reach the retroreflectivesubstrate 102 and can be reflected back through the coating 104 to thesource 114 as returned visible electromagnetic radiation 112. Thereturned visible electromagnetic radiation 112 can be traveling in athird vector substantially parallel to the direction of a fourth vectorthat visible electromagnetic radiation 110 is traveling. The thirdvector can be in a direction opposite of a direction of the fourthvector. The visible electromagnetic radiation source 114 c can be acomponent of the same system as or a component of a different systemfrom the NIR electromagnetic radiation source 114 a. The source 114 cancomprise an automobile, the visible electromagnetic radiation source 114c can comprise a headlight of the automobile, and the NIRelectromagnetic radiation source 114 a and NIR detector 114 b can bepart of a LIDAR system.

Due to the minimal, if any, absorption or scattering of the visibleelectromagnetic radiation 110 by the coating 104 the returned visibleelectromagnetic radiation 112 has a substantially similar magnitudecompared to a magnitude of the visible electromagnetic radiation 110.The substantially similar magnitude can enable observation of theretroreflective substrate 102 by an operator and/or a visibleelectromagnetic radiation detector.

The coating 104 can be suitable to scatter and/or absorb NIRelectromagnetic radiation and reduce the NIR retroreflectance of theretroreflective substrate 102. The NIR retroreflectance of theretroreflective substrate 102 can be reduced by 20% or greater such as,reduced by 30% or greater, reduced by 40% or greater, reduced by 50% orgreater, reduced by 60% or greater, reduced by 70% or greater, reducedby 80% or greater, reduced by 90% or greater, or reduced by 99% orgreater. The NIR retroreflectance of the retroreflective substrate 102can be reduced by 100% or lower, such as, reduced by 99% or lower,reduced by 90% or lower, reduced by 80% or lower, reduced by 70% orlower, reduced by 60% or lower, reduced by 50% or lower, reduced by 40%or lower, or reduced by 30% or lower. The reduction in NIRretroreflectance of the retroreflective substrate 102 can be in a rangeof 20% to 100%, such as, 20% to 99%, 20% to 90%, 20% to 80%, 20% to 70%,20% to 50%, 20% to 30%, 30% to 100%, 30% to 99%, 30% to 90%, 30% to 70%,50% to 100%, 50% to 90%, 50% to 99%, 70% to 90%, 70% to 99%, or 70% to100%.

The NIR retroreflectance of the retroreflective substrate 102 can bereduced in a wavelength range of 800 nm to 2000 nm, such as, 800 nm to1600 nm. The NIR retroreflectance of the retroreflective substrate 102can be reduced at various NIR wavelengths, such as, 905 nm and/or 1550nm. The coating 104 can absorb and/or scatter the 905 nm wavelengthand/or the 1550 nm wavelength. The coating 104 can comprise a 905 nmabsorbance of 0.05 absorbance unit(s) (Au) or greater such as, 0.1 Au orgreater, 0.2 Au or greater, 0.3 Au or greater, 0.4 Au or greater, 0.5 Auor greater, 0.6 Au or greater, 0.7 Au or greater, 0.8 Au or greater, 0.9Au or greater, 1 Au or greater, or 2 Au or greater. The coating 104 cancomprise a 905 nm absorbance of 2 Au or lower, such as, 1 Au or lower,0.9 Au or lower, 0.8 Au or lower, 0.7 Au or lower, 0.6 Au or lower, 0.5Au or lower, 0.4 Au or lower, 0.3 Au or lower, 0.2 Au or lower, or 0.1Au or lower. The coating 104 can comprise a 905 nm absorbance in therange of 0.05 Au to 2 Au such as, 0.1 Au to 2 Au, 0.2 Au to 2 Au, 0.4 Auto 2 Au, 0.6 Au to 2 Au, 0.8 Au to 2 Au, 0.1 Au to 0.9 Au, 0.2 Au to 0.9Au, 0.4 Au to 0.9 Au, 0.6 Au to 0.9 Au, 0.2 Au to 0.8 Au, or 0.3 Au to0.8 Au.

The coating 104 can comprise a 1550 nm absorbance of 0.05 Au or greatersuch as, 0.1 Au or greater, 0.2 Au or greater, 0.3 Au or greater, 0.4 Auor greater, 0.5 Au or greater, 0.6 Au or greater, 0.7 Au or greater, 0.8Au or greater, 0.9 Au or greater, or 2 Au or greater. The coating 104can comprise a 1550 nm absorbance of 2 Au or lower, such as, 1 Au orlower, 0.9 Au or lower, 0.8 Au or lower, 0.7 Au or lower, 0.6 Au orlower, 0.5 Au or lower, 0.4 Au or lower, 0.3 Au or lower, 0.2 Au orlower, or 0.1 Au or lower. The coating 104 can comprise a 1550 nmabsorbance in the range of 0.05 Au to 2 Au such as, 0.1 Au to 2 Au, 0.2Au to 2 Au, 0.4 Au to 2 Au, 0.6 Au to 2 Au, 0.8 Au to 2 Au, 0.1 Au to0.9 Au, 0.2 Au to 0.9 Au, 0.4 Au to 0.9 Au, 0.6 Au to 0.9 Au, 0.2 Au to0.8 Au, or 0.3 Au to 0.8 Au.

As used herein, an “absorbance unit” or “Au” refers to a base 10logarithm of a ratio of the electromagnetic radiation received by asubstance to the electromagnetic radiation transmitted by the substance.

Minimal, if any, absorption or scattering of visible electromagneticradiation by the coating 104 coupled with substantial adsorption and/orscattering of NIR electromagnetic radiation by the coating 104, canenable the coating 104 to reduce the NIR retroreflectance of theretroreflective substrate 102 greater than the visible retroreflectanceof the retroreflective substrate 102. The coating 104 can comprise aratio of reduction in electromagnetic radiation retroreflectance at awavelength of 905 nm and/or 1550 nm to reduction in electromagneticradiation retroreflectance averaged over a wavelength range of 400 nm to700 nm of 2:1 or greater, such as, 4:1 or greater, 10:1 or greater, or20:1 or greater. The coating 104 can comprise a ratio of reduction inelectromagnetic radiation retroreflectance at a wavelength of 905 nmand/or 1550 nm to reduction in electromagnetic radiationretroreflectance averaged over a wavelength range of 400 nm to 700 nm of40:1 or lower, such as, 20:1 or lower, 10:1 or lower, or 4:1 or lower.The coating 104 can comprise a ratio of reduction in electromagneticradiation retroreflectance at a wavelength of 905 nm and/or 1550 nm toreduction in electromagnetic radiation retroreflectance averaged over awavelength range of 400 nm to 700 nm of 2:1 to 40:1 such as, 2:1 to20:1, 2:1 to 10:1, 2:1 to 4:1, 4:1 to 20:1, 4:1 to 10:1, 10:1 to 20:1,or 10:1 to 40:1. The reduction in electromagnetic radiationretroreflectance can be based on the retroreflectance of theretroreflective substrate 102 devoid of the coating 104. For example,the reduction in retroreflectance can be determined by measuring theretroreflectance of the retroreflective substrate 102 devoid of thecoating 104, measuring the retroreflectance of the article 100comprising both the retroreflective substrate 102 and the coating 104,and determining the difference between the two measurements.

The coating 104 can comprise a ratio of electromagnetic radiationextinction at a wavelength of 905 nm and/or 1550 nm to electromagneticradiation extinction averaged over a wavelength range of 400 nm to 700nm of 2:1 or greater, such as, 4:1 or greater, 10:1 or greater, or 20:1or greater. The coating 104 can comprise a ratio of electromagneticradiation extinction at a wavelength of 905 nm and/or 1550 nm toelectromagnetic radiation extinction averaged over a wavelength range of400 nm to 700 nm of 40:1 or lower, such as, 20:1 or lower, 10:1 orlower, or 4:1 or lower. The coating 104 can comprise a ratio ofelectromagnetic radiation extinction at a wavelength of 905 nm and/or1550 nm to electromagnetic radiation extinction averaged over awavelength range of 400 nm to 700 nm of 2:1 to 40:1 such as, 2:1 to20:1, 2:1 to 10:1, 2:1 to 4:1, 4:1 to 20:1, 4:1 to 10:1, 10:1 to 20:1,or 10:1 to 40:1.

The reduction in electromagnetic radiation retroreflectance in the NIRrange and the increase in electromagnetic extinction can be a result ofNIR absorption and/or NIR scattering. The coating 104 can comprise aratio of electromagnetic radiation absorption at a wavelength of 905 nmand/or 1550 nm to electromagnetic radiation absorption averaged over awavelength range of 400 nm to 700 nm of 2:1 or greater, such as, 4:1 orgreater, 10:1 or greater, or 20:1 or greater. The coating 104 cancomprise a ratio of electromagnetic radiation absorption at a wavelengthof 905 nm and/or 1550 nm to electromagnetic radiation absorptionaveraged over a wavelength range of 400 nm to 700 nm of 40:1 or lower,such as, 20:1 or lower, 10:1 or lower, or 4:1 or lower. The coating 104can comprise a ratio of electromagnetic radiation absorption at awavelength of 905 nm and/or 1550 nm to electromagnetic radiationabsorption averaged over a wavelength range of 400 nm to 700 nm of 2:1to 40:1 such as, 2:1 to 20:1, 2:1 to 10:1, 2:1 to 4:1, 4:1 to 20:1, 4:1to 10:1, 10:1 to 20:1, or 10:1 to 40:1.

The coating 104 can comprise a ratio of electromagnetic radiationscattering at a wavelength of 905 nm and/or 1550 nm to electromagneticradiation scattering averaged over a wavelength range of 400 nm to 700nm of at least 2:1, such as, 4:1, at least 10:1, or at least 20:1. Thecoating 104 can comprise a ratio of electromagnetic radiation scatteringat a wavelength of 905 nm and/or 1550 nm to electromagnetic radiationscattering averaged over a wavelength range of 400 nm to 700 nm of 40:1or lower, such as, 20:1 or lower, 10:1 or lower, or 4:1 or lower. Thecoating 104 can comprise a ratio of electromagnetic radiation scatteringat a wavelength of 905 nm and/or 1550 nm to electromagnetic radiationscattering averaged over a wavelength range of 400 nm to 700 nm of 2:1to 40:1 such as, 2:1 to 20:1, 2:1 to 10:1, 2:1 to 4:1, 4:1 to 20:1, 4:1to 10:1, 10:1 to 20:1, or 10:1 to 40:1. The electromangetic radiationabsorption, electromangetic radiation scattering, electromangeticradiation extinction, electromangetic radiation transmittance, andelectromangetic radiation retroreflectance of the coating 104 can bemeasured in the cured state of the coating 104.

As used herein, “average over a wavelength range of 400 nm to 700 nm”can include measuring a parameter (e.g., retroreflectance, extinction,absorption, scattering, transmittance) over the wavelength range of 400nm to 700 nm in 1 nm steps (e.g., 301 total measurements) and thentaking an average of the measurements.

The scattering and/or absorption of visible electromagnetic radiation bythe coating 104 can affect the observed color of the retroreflectivesubstrate 102. A visible color of the retroreflective substrate 102 withthe coating 104 and a visible color of the retroreflective substrate 102without the coating 104 can be compared to determine a color difference,ΔE. The color difference, ΔE, can be minimized in order to limitobservable visible color changes to the retroreflective substrate 102after deposition of the coating composition to form coating 104.

The color difference, ΔE, can be measured using the InternationalCommission on Illumination L*a*b* (CIELAB) color space. The CIELAB colordifference, ΔE, values reported herein are determined using anintegrating sphere with D65 Illumination, 10° observer with specularcomponent included according to ASTM E308 unless otherwise stated. TheCIELAB color difference, ΔE, is the difference between two colors in theCIELAB color space based on the difference between collected values ofL*, a*, and b* according to Equation 1.

ΔE=√{square root over ((ΔL*)²+(Δα*)²+(Δb*)²)}

The coating 104 can have a CIELAB color difference, ΔE, of the visiblecolor of the retroreflective substrate without the coating 104 comparedto the visible color of the retroreflective substrate with the coatingof 25 or lower, such as, 20 or lower, 15 or lower, 10 or lower, 5 orlower, 2 or lower, or 1 or lower, all as measured using an integratingsphere with D65 Illumination, 10° observer with specular componentincluded. The coating 104 can have a CIELAB color difference, ΔE, of thevisible color of the retroreflective substrate without the coating 104compared to the visible color of the retroreflective substrate with thecoating 104 of 0 or greater, such as, 1 or greater, 2 or greater, 5 orgreater, 10 or greater, 15 or greater, or 20 or greater, all as measuredusing an integrating sphere with D65 Illumination, 10° observer withspecular component included. The coating 104 can have a CIELAB colordifference, ΔE, of the visible color of the retroreflective substratewithout the coating 104 compared to the visible color of theretroreflective substrate with the coating 104 in a range of 0 to 25,such as, 1 to 20, 1 to 15, 1 to 10, 5 to 10, or 2 to 10, all as measuredusing an integrating sphere with D65 Illumination, 10° observer withspecular component included.

EXAMPLES

The present disclosure will be more fully understood by reference to thefollowing examples, which provide illustrative non-limiting aspects ofthe invention. It is understood that the invention described in thisspecification is not necessarily limited to the examples described inthis section.

As used herein, the term “Mw” refers to the average molecular weight andmeans the theoretical value as determined by Gel PermeationChromatography using Waters 2695 separation module with a Waters 410differential refractometer (RI detector) and polystyrene standards. TheMw values reported according to the present disclosure were determinedusing this method. Tetrahydrofuran was used as the eluent at a flow rateof 1 ml min-1, and two PL Gel Mixed C columns were used for separation.

As used herein, the term “parts” refers to parts by weight unlessindicated to the contrary.

Example A: Preparation of Acrylic Polymer A

TABLE 1 Polymer A component composition Charge Ingredients Parts byweight #1 VM&P Naphtha 431.0 #2 t-amyl peroxy-2-ethylhexanoate 22.6butyl acetate 153.1 #3 styrene 452.4 2-ethylhexyl acrylate 301.6 butylmethacrylate 294.1 methyl methacrylate 271.4 hydroxyethyl acrylate 150.8methacrylic acid 28.7 acrylic acid 9.0 t-dodecyl mercaptan 19.6 #4 VM&PNaphtha 83.5 isobutnaol 27.8 #5 t-amyl peroxy-2-ethylhexanoate 7.5 VM&PNaphtha 114.4 isobutanol 41.8 #6 VM&P Naphtha 306.2 isobutanol 236.6 #7propylene imine 6.3 #8 tetraethylene entamine 6.0 #9 DESMODUR ® N 3390ABA/SN 29.0 butyl acetate 50.0

To prepare polymer A, charge 1 was added to a round bottom flaskequipped with a stirrer, condenser, temperature control system, and twofeeding lines under inert gas. The reaction mixture was heated to 126°C. with stirring. Charge 2 was mixed together and added into thereaction mixture over 180 minutes. At the same time, charge 3 was addedinto the reaction mixture over 180 minutes. When the addition of charge2 and 3 were completed, charge 4 was used to rinse charge 2 and 3. Afteraddition of charge 4, an additional spike (charge 5) of initiator wasadded to the reaction mixture over one hour and stirring was continuedfor one hour at reflux conditions. After completion of stirring charge 6was added and the reaction mixture was cooled to 60° C. At 60° C.,charge 7 was added into reaction mixture and stirring continued for onehour. After completion of stirring, the reaction mixture was cooled to40° C. At 40° C., charge 8 was added into the reaction mixture and thestirring continued for 10 minutes. After stirring at 40° C., charge 9was added into reactor over one hour. After addition of charge 9, thereaction mixture was poured out. The solid of acrylic polymer A is 51.5%by weight and the Mw of polymer A is 20000.

Example B: Preparation of Acrylic Polymer B

TABLE 2 Polymer B component composition Charge Ingredients Parts byweight #1 VM&P Naphtha 275.7 Isobutanol 214.0 #2 VAZO 67 2,2′-Azodi(2-9.46 methylbutyronitrile) Toluene 155.8 #3 hydroxyethyl acrylate 157.2methyl methacrylate 292.0 2-ethylhexyl acrylate 314.4 butyl methacrylate306.6 Styrene 471.6 methacrylic acid 30.4 t-dodecyl mercaptan 18.4 VM&PNaphtha 3.2 #4 VM&P Naphtha 49.8 #5 VAZO 67 2,2′-Azodi(2- 9.4methylbutyronitrile) VM&P Naphtha 147.7 #6 VM&P Naphtha 23.2 #7 VM&PNaphtha 511.0 #8 Isobutanol 118.0

To prepare polymer B, charge 1 was added to a round bottom flaskequipped with a stirrer, condenser, temperature control system, and twofeeding lines under inert gas. 39.30% by weight of charge 2 and 39.30%by weight of charge 3 were added into the reaction mixture of charge 1at the same time. The reaction mixture was heated to reflux (112° C.)with stirring. The remainder of charge 2 and charge 3 were added intothe reaction mixture over two hours separately. After addition of charge2 and charge 3, charge 4 was used to rinse the feed lines of bothcharges 2 and 3. At reflux conditions, an additional spike (charge 5) ofinitiator was added to the reaction mixture over three hours. Afteraddition of charge 5, charge 6 was used to rinse and stirring wascontinued for 30 minutes at reflux conditions. After stirring completed,heat was off and charge 7 was added into reaction mixture. At 80° C.,charge 8 was added into reactor to cool the reaction mixture to 40° C.The solid of acrylic polymer B is 50.8% by weight and the Mw of polymerB is 22000.

Example 1

To prepare coating ATO-1, 2 parts Antimony Tin Oxide (ATO) (e.g.,pigment), (SN902SD, Nano Technologies Inc.) were mixed with 8 partspolymer A, 11 parts n-butyl acetate, and 109 parts Zirconox millingmedia (1-1.2 mm Zirconox milling beads, JYOTI Ceramics.). The mixturewas dispersed by shaking in a DAS 200 disperser (Lau GmbH) for fourhours, and the milling media was removed by filtering with a 325 μmpaper cone filter. Then 4.8 parts of the ATO dispersion was mixed with5.2 parts TMAC9000FR clearcoat (available from PPG, Pittsburgh, Pa.)(e.g., film-forming resin) to form coating ATO-1 and drawdown on atransparent Mylar film using a #44 wire-wound drawdown bar from RDSpecialties, Webster, New York, resulting in a wet film thickness of 4.4mils (112 μm).

To prepare coating ATO-2, 2 parts ATO (e.g., pigment) were mixed with 8parts of an acrylic dispersant as described in U.S. Pat. No. 8,129,466(Synthesis Example A), 12 parts n-butyl acetate, and 45 parts glassbeads (2227 Spheriglass, Part number 602498 from Potters Industries,LLC). The mixture was dispersed by shaking in a DAS 200 disperser (LauGmbH) for 16 hours, and the glass beads were removed by filtering with a55 μm bag filter (33-NMP 55 X1R-B, Brown and O'Malley Co.). Then, 4.7parts of the solution was mixed with 5.3 parts TMAC9000FR clearcoat toform coating ATO-2 and drawdown on a transparent Mylar film using a #44wire-wound drawdown bar from RD Specialties resulting in a wet filmthickness of 4.4 mils (112 μm).

The ATO-containing coatings ATO-1 and ATO-2 were tested fortransmittance and extinction utilizing a Perkin Elmer Lambda 950UV-VisNIR spectrometer, and the results of the transmittance are plotted inFIG. 2 and the results of the extinction are plotted in FIG. 3. Thecoatings ATO-1 and ATO-2 have a strong NIR electromagnetic radiationextinction, including an extinction at 905 nm and 1550 nm. The coatingsATO-1 and ATO-2 reduced 905 nm transmission by 30% and 1550 nmtransmission by 80% while maintaining 80%-90% visible transmissionaveraged over the visible range of the electromagnetic spectrum.

Particle size of the milled ATO was analyzed by dynamic lightscattering, using a Nano ZS instrument manufactured by Malvern,Westborough, Mass. ATO-2 was determined to have an average particle sizeof 43 nm, and ATO-1 was 215 nm. Due to the use of longer grind time,finer media size, and different dispersant, ATO-2 has a smaller particlesize than ATO-1.

Extinction was calculated based on percent transmission, and the resultsare shown in Table 3 herein. Coating ATO-2 has a higher ratio of NIRelectromagnetic extinction to visible electromagnetic extinction versuscoating ATO-1. The higher ratio suggests that reducing particle size tonanoscale was effective at increasing the ratio of NIR electromagneticradiation extinction to visible electromagnetic radiation extinction asmeasured at 905 nm, Ex₉₅₀/Ex_(vis), and 1550 nm, Ex₁₅₅₀/Ex_(vis). It isbelieved that a further reduction in particle size may additionallyincrease the ratio of NIR electromagnetic radiation extinction tovisible electromagnetic radiation extinction, and other pigments mayexhibit an increase in the ratio of NIR electromagnetic radiationextinction to visible electromagnetic radiation extinction by reducingparticle size. It is believed that coatings containing ATO have areduced NIR transmittance via extinction of NIR electromagneticradiation.

As used herein, “Ex₉₅₀/Ex_(vis)” is defined to refer to the ratio ofelectromagnetic radiation extinction at 905 nm to the averagedelectromagnetic radiation extinction over the visible range of 400 nm to700 nm with measurements taken in 1 nm steps. As used herein,“Ex₁₅₅₀/Ex_(vis)” is defined to refer to the ratio of electromagneticradiation extinction at 1550 nm to the averaged electromagneticradiation extinction over the visible range of 400 nm to 700 nm withmeasurements taken in 1 nm steps.

Example 2

To prepare coating LaB₆-1, 2.2 parts LaB₆ (Skysprings NanomaterialsInc., 99.0+%, average particle size (APS): 50-80 nm) was mixed with 8.5parts polymer A and 11 parts n-butyl acetate and 109 parts Zirconoxmilling media (1-1.2 mm Zirconox milling beads, JYOTI Ceramics.). Themixture was dispersed by shaking in a DAS 200 disperser (Lau GmbH) forfour hours, and the milling media was removed by filtering with a 325 μmpaper cone filter. Then 3 parts of the obtained LaB₆ dispersion wasmixed with 433 parts TMAC9000FR clearcoat to form coating LaB₆-1 anddrawdown using a #44 wire-wound drawdown bar from RD Specialties on atransparent Mylar film resulting in a wet film thickness of 4.4 mils(112 μm).

To prepare coating LaB₆-2, 2 parts LaB₆ (Skysprings Nanomaterials Inc.,99.0+%, APS: 50-80 nm) were mixed with an acrylic dispersant asdescribed in U.S. Pat. No. 8,129,466 (Synthesis Example A), 12 partsn-butyl acetate, and 45 parts glass beads (2227 Spheriglass, Part number602498 from Potters Industries, LLC). The mixture was dispersed byshaking in a DAS 200 disperser (Lau GmbH) for 16 hours, and the mediawas removed by filtering with a 55 μm bag filter (33-NMP 55 X1R-B, Brownand O'Malley Co.). Then 2.4 parts of the LaB₆ dispersion was mixed with27.6 parts TMAC9000FR clearcoat to form coating LaB₆-2 and drawdown on atransparent Mylar film using a #44 wire-wound drawdown bar from RDSpecialties resulting in a wet film thickness of 4.4 mils (112 μm).

The LaB₆-containing coatings LaB₆-1 and LaB₆-2 were tested fortransmittance and extinction utilizing a Perkin Elmer Lambda 950UV-VisNIR spectrometer, and the transmittance results are plotted in FIG. 4and the extinction results are plotted in FIG. 5. LaB₆-containingcoatings LaB₆-1 and LaB₆-2 have a strong extinction near 905 nm. Due tothe use of longer grind time, finer media size and different dispersant,coating LaB₆-2 has a smaller particle size than coating LaB₆-1. Dynamiclight scattering measurement, using a Nano ZS instrument, shows thatLaB₆-2 has an average particle size of 119 nm, much smaller than LaB₆-1with 2401 nm particles. As shown in Table 1, coating LaB₆-2 had a higherratio of NIR electromagnetic radiation extinction to visibleelectromagnetic radiation extinction than coating LaB₆-1. Similar to thecase of ATO, the result demonstrates that reducing the particle size tonanoscale increases the ratio of NIR electromagnetic radiationextinction to visible electromagnetic radiation extinction as measuredat 905 nm, Ex₉₅₀/Ex_(vis), and 1550 nm, Ex₁₅₅₀/Ex_(vis).

The LaB₆-2 films reduced 905 nm transmission by 20% while maintainingmore than 90% (10% reduction) visible transmission. Coating LaB₆-2resulted in a ratio of reduction in NIR transmittance (e.g., LIDARsignal wavelength) to visible transmittance of 2. It is believed thatcoatings containing LaB₆ reduce the NIR transmittance via extinction ofNIR electromagnetic radiation.

TABLE 3 Extinction of LaB₆ and ATO-containing samples 905 nm 1550 nmAveraged extinction/ extinction/ extinction Extinction Extinctionaveraged averaged in visible at at extinction extinction Sample (400-700nm) 905 nm 1550 nm in visible in visible ATO-1 0.11 0.18 1.01 1.70 9.59ATO-2 0.08 0.16 0.92 1.91 11.23 LaB₆-1 0.04 0.09 0.008 2.08 0.19 LaB₆-20.04 0.11 0.015 3.05 0.43

Example 3

1.5 part LaB₆ powder (e.g., pigment) (Skysprings Nanomaterials Inc.,99.0+%, APS: 50-80 nm) was mixed with 5 parts acrylic resin as describedin U.S. Pat. No. 8,129,466 (Synthesis Example A), 45 parts glass beads(2227 Spheriglass, Part number 602498 from Potters Industries, LLC), and15 parts n-butyl acetate. The mixture was dispersed in a DAS 200disperser (Lau GmbH) for 16 hours, and the glass beads were removed byfiltering with a 55 μm bag filter (33-NMP 55 X1R-B, Brown and O'MalleyCo.) to form a LaB₆ dispersion.

6 parts of the LaB₆ dispersion were mixed with 88 parts DC2000 refinishclearcoat (available from PPG, Pittsburgh, Pa.) and 6 parts n-butylacetate to formulate a coating LaB₆-3. 8 parts of LaB₆ dispersion weremixed with 86 parts DC2000 refinish clearcoat and 5 parts n-butylacetate to formulate a coating LaB₆-4. Liquid coating LaB₆-3 and LaB₆-4were each applied on a retroreflective sheet (Nikkalite 92802) bydrawdown using a #44 wire-wound drawdown bar from RD Specialtiesresulting in a wet film thickness of 4.4 mils (112 μm). The coatingsLaB₆-3 and LaB₆-4 were each cured on the respective retroreflectivesheet at ambient conditions and were tested for LIDAR signal intensityand retroreflectivity. The LIDAR signal was tested with a LeddarVu 8solid state LIDAR, which utilizes 905 nm NIR light source. The LIDARsignal was read at 10 m detector-to-sample distance with laser intensitysetting at 6%. The visible retroreflectance (reflectivity) was evaluatedwith a 922 RoadVista retroreflectometer which is ASTM E1709 compliant.

For coating LaB₆-3 (e.g., contains 0.9% by weight LaB₆), the reductionin LIDAR signal is 44% while visible retroreflectance is maintained at92% (8% reduction) with respect to uncoated retroreflective sheet.Coating LaB₆-3 resulted in a ratio of reduction in NIR retroreflectance(e.g., LIDAR signal) to visible retroreflectance of 5.5. For coatingLaB₆-4 (e.g., contains 1.2% by weight LaB₆), the reduction in LIDARsignal is 60% while visible retroreflectance is maintained at 88% (12%reduction) with respect to the uncoated retroreflective sheet. CoatingLaB₆-3 resulted in a ratio of reduction in NIR retroreflectance (e.g.,LIDAR signal) to visible retroreflectance of 5.

Comparative Example 4

To produce comparative coating Ep-1 (e.g., containing 0.08% by weightEpolight 5547 dye), 1 part Epolight 5547 dye was dissolved in 99 partsmethyl amyl ketone. Epolight 5547 dye comprises a phthalocyanine dye.Then, 4 parts Epolight 5547 dye solution was mixed with 96 parts DC2000liquid clearcoat. The coating mixture was applied on a retroreflectivesheet (Nikkalite 92802) via drawdown using a #44 wire-wound drawdown barfrom RD Specialties resulting in a wet film thickness of 4.4 mils (112μm). Comparative coating EP-1 was cured on the retroreflective sheet atambient conditions and was tested for LIDAR signal intensity andretroreflectivity.

Comparative coating Ep-1 reduces 33% LIDAR signal while visibleretroreflectance is maintained at 100% with respect to the uncoatedretroreflective sheet. Comparative coating Ep-1 resulted in a ratio ofreduction in NIR retroreflectance (e.g., LIDAR signal) to visibleretroreflectance of greater than 50.

Example 5

Coating A1-1 was prepared and tested for a ratio of reduction in NIRretroreflectance (e.g., LIDAR signal) to visible retroreflectance. 11parts Alumina powder (5 um spherical particles, 26R-8505, Inframat)(e.g., pigment) was mixed with 7.5 parts acrylic resin Polymer B and 11parts n-butyl acetate solvent. The mixture was stirred for 20 minutes toobtain an alumina dispersion.

3 parts alumina dispersion was mixed with 97 parts DC2000 clearcoat, andthe mixture was drawdown on a retroreflective sheet using a #44wire-wound drawdown bar from RD Specialties. Coating A1-1 was cured onthe retroreflective sheet at ambient conditions and was tested for LIDARsignal intensity and retroreflectivity.

Coating A1-1 reduces LIDAR signal by 23% while visible retroreflectanceis maintained at 94% (6% reduction) with respect to the uncoatedretroreflective sheet. Coating A1-1 resulted in a ratio of reduction inNIR retroreflectance (e.g., LIDAR signal) to visible retroreflectance of3.9. It is believed that coating A1-1 reduced the NIR retroreflectancevia scattering of NIR electromagnetic radiation.

Example 6

To produce coating Au-1, 50 parts aqueous dispersion of Au nanorods(0.035 mg/mL, A12-10-900-CTAB, Nanopartz) was mixed with 1 part resin(U.S. Pat. No. 9,598,597 Example 1). The solution was drop-cast onto aMylar substrate. Coating Au-1 was cured on the retroreflective sheet atambient conditions.

Coating Au-1 was tested for transmittance utilizing a Vernier Go DirectSpectroVis Plus spectrometer, and the transmittance results are plottedin FIG. 6. The NIR transmission drops to 75% (25% reduction) and visibletransmission is above 90% (10% reduction). The coating Au-1 containingAu nanorods results in a ratio of reduction in NIR transmittance (e.g.,LIDAR signal wavelength) to visible transmittance of greater than 2.5.

Example 7

Coating LaB₆-2 and comparative coating Ep-1 were tested forweather-ability. The coatings were cured on a white colored aluminumpanel (Tru aluminum 04X12X038, unpolished, white, APT33676, Batch:20814216, ACT Laboratories Inc.) and placed into a weather-o-meter(following SAE J2527) for 250 to 500 hours. Then, the film was testedfor reflectivity utilizing a Perkin Elmer Lambda 950UV-Vis NIRspectrometer. The NIR electromagnetic radiation extinction of thecomparative coating Ep-1containing films deteriorated quickly such thatafter 250 h, no pronounced electromagnetic radiation extinction can beseen in the NIR. After 500 hours of weathering, coating LaB₆-2 did nothave an observable NIR electromagnetic radiation extinction signaldeterioration as shown in FIG. 7. It is believed that the pigment inLaB₆-2 enables the enhanced weather resistance as compared tocomparative coating Ep-1 which contains a dye.

Example 8

Coating LaB₆-2 was sprayed over stop signs (engineering-grade officialMUTCD stop signs, RoadTrafficSigns.com). A stainless steel substrate wassprayed at the same time for determination of dry film thickness with aDeltascope MP30.

An integrating sphere spectrophotometer (Minolta CM-3600d) with D65Illumination, 10° observer with specular component included according toASTM E308 was used to evaluate the color difference, CIELAB ΔE, of thecoating LaB₆-2. Values of ΔE were calculated according to Equation 1 andare shown in Table 4.

TABLE 4 Color measurement of coated stop signs % reduction in NIR retro-Coating reflectance LaB₆ thickness (LIDAR signal Measured partconcentration (μm) ΔE intensity) White Letter 1.2% 10 13.54 50% 1.2% 2321.28 70% Red Background 1.2% 10 12.00 50% 1.2% 23 20.18 70%

As shown in Table 3, coating LaB₆-2 reduced the NIR retroreflectance ofthe retroreflective substrate and maintained a sufficient level ofvisible retroreflectance and as shown in Table 4. The coating LaB₆-2 didnot significantly alter the color of the substrate (e.g., stop sign). Itis believed that other coatings formulations according to the presentdisclosure also can achieve a reduction in NIR retroreflectance, canmaintain a sufficient level of visible retroreflectance, and may notsignificantly alter the color of the underlying layers or substrate.

One skilled in the art will recognize that the herein describedcompositions, articles, methods, and the discussion accompanying themare used as examples for the sake of conceptual clarity and that variousconfiguration modifications are contemplated. Consequently, as usedherein, the specific exemplars set forth and the accompanying discussionare intended to be representative of their more general classes. Ingeneral, use of any specific exemplar is intended to be representativeof its class, and the non-inclusion of specific components (e.g.,operations), devices, and objects should not be taken as limiting.

With respect to the appended claims, those skilled in the art willappreciate that recited operations therein may generally be performed inany order. Also, although various operational flows are presented in asequence(s), it should be understood that the various operations may beperformed in other orders than those which are illustrated or may beperformed concurrently. Examples of such alternate orderings may includeoverlapping, interleaved, interrupted, reordered, incremental,preparatory, supplemental, simultaneous, reverse, or other variantorderings, unless context dictates otherwise. Furthermore, terms like“responsive to,” “related to,” or other past-tense adjectives aregenerally not intended to exclude such variants, unless context dictatesotherwise.

Although various examples have been described herein, manymodifications, variations, substitutions, changes, and equivalents tothose examples may be implemented and will occur to those skilled in theart. Also, where materials are disclosed for certain components, othermaterials may be used. It is therefore to be understood that theforegoing description and the appended claims are intended to cover allsuch modifications and variations as falling within the scope of thedisclosed examples. The following claims are intended to cover all suchmodification and variations.

Various aspects of the invention according to the present disclosureinclude, but are not limited to, the aspects listed in the followingnumbered clauses.

-   1. A coating composition for application over a retroreflective    substrate, comprising:    -   a resin; and    -   a pigment suitable to absorb and/or scatter electromagnetic        radiation in a wavelength range of 800 nm to 2000 nm;    -   wherein a coating formed from the coating composition comprises        a ratio of reduction in electromagnetic radiation        retroreflectance at a wavelength of 905 nm and/or 1550 nm to        reduction in electromagnetic radiation retroreflectance averaged        over a wavelength range of 400 nm to 700 nm of at least 2:1.-   2. The coating composition of clause 1, wherein the coating    comprises a ratio of reduction in electromagnetic radiation    retroreflectance at a wavelength of 905 nm and/or 1550 nm to    reduction in electromagnetic radiation retroreflectance averaged    over a wavelength range of 400 nm to 700 nm of at least 4:1.-   3. The coating composition of any one of clauses 1-2, wherein the    coating comprises a ratio of electromagnetic radiation extinction at    a wavelength of 905 nm and/or 1550 nm to electromagnetic radiation    extinction averaged over a wavelength range of 400 nm to 700 nm of    at least 2:1.-   4. The coating composition of any one of clauses 1-3, wherein the    coating comprises a ratio of electromagnetic radiation extinction at    a wavelength of 905 nm and/or 1550 nm to electromagnetic radiation    extinction averaged over a wavelength range of 400 nm to 700 nm of    at least 4:1.-   5. The coating composition of any one of clauses 1-4, wherein the    coating comprises a ratio of electromagnetic radiation absorption at    a wavelength of 905 nm and/or 1550 nm to electromagnetic radiation    absorption averaged over a wavelength range of 400 nm to 700 nm of    at least 2:1.-   6. The coating composition of any one of clauses 1-5, wherein the    coating comprises a ratio of electromagnetic radiation scattering at    a wavelength of 905 nm and/or 1550 nm to electromagnetic radiation    scattering averaged over a wavelength range of 400 nm to 700 nm of    at least 2:1.-   7. The coating composition of any one of clauses 1-6, wherein the    pigment comprises at least one of zinc oxide, alumina, antimony tin    oxide, tungsten oxide, gold nanoparticles, silver nanoparticles,    copper nanoparticles, lanthanum hexaboride, dicopper hydroxide    phosphate, and a phthalocyanine.-   8. The coating composition of any one of clauses 1-7, wherein the    pigment comprises lanthanum hexaboride.-   9. The coating composition of any one of clauses 1-8, wherein the    pigment comprises an average particle size of 1 nm to 5000 nm.-   10. The coating composition of any one of clauses 1-9, wherein the    pigment comprises an average particle size of 10 nm to 150 nm.-   11. The coating composition of any one of clauses 1-10, wherein the    coating absorbs at least 0.1 absorbance units of electromagnetic    radiation at a wavelength of 905 nm.-   12. The coating composition of any one of clauses 1-11, wherein the    coating absorbs at least 0.2 absorbance units of electromagnetic    radiation at a wavelength of 1550 nm.-   13. A system comprising:    -   the coating composition of any one of clauses 1-12 disposed over        a retroreflective substrate, wherein the system comprises a        CIELAB color difference, ΔE, of 25 or less when compared to the        retroreflective substrate without the coating, as measured using        an integrating sphere with D65 Illumination, 10° observer with        specular component included.-   14. The system of clause 13, wherein the retroreflective substrate    comprises at least one of a tape, a sign, a vehicle, a marker, and    clothing.-   15. The coating composition of any one of clauses 1-12 and/or the    system of any one of clauses 13-14, wherein the resin comprises at    least one of a thermosetting film-forming resin and a thermoplastic    film-forming resin.-   16. The coating composition of any one of clauses 1-12 and 15 and/or    the system of any one of clauses 13-14, wherein the resin further    comprises at least one of acrylic polymers, polyester polymers,    polyurethane polymers, polyamide polymers, polyether polymers,    polysiloxane polymers, copolymers thereof, and mixtures thereof.-   17. The coating composition of any one of clauses 1-12 and 15-16    and/or the system of any one of clauses 13-14, wherein the coating    transmits 80 percent or less of electromagnetic radiation at a    wavelength of 905 nm.-   18. A method for producing a retroreflective article with reduced    electromagnetic radiation retroreflection at a wavelength of 905 nm    and/or 1550 nm, the method comprising:    -   depositing a coating composition over a retroreflective        substrate to form a coating, the coating composition comprising:        -   a resin; and        -   a pigment suitable to absorb and/or scatter electromagnetic            radiation in a wavelength range of 800 nm to 2000 nm;        -   wherein the coating comprises a ratio of reduction in            electromagnetic radiation retroreflectance at a wavelength            of 905 nm and/or 1550 nm to reduction in electromagnetic            radiation retroreflectance averaged over a wavelength range            of 400 nm to 700 nm of at least 2:1.-   19. A retroreflective article comprising:    -   a retroreflective substrate; and    -   a coating disposed over the retroreflective substrate, the        coating comprising:        -   a resin; and        -   a pigment suitable to absorb and/or scatter electromagnetic            radiation in a wavelength range of 800 nm to 2000 nm;        -   wherein the coating comprises a ratio of reduction in            electromagnetic radiation retroreflectance at a wavelength            of 905 nm and/or 1550 nm to reduction in electromagnetic            radiation retroreflectance averaged over a wavelength range            of 400 nm to 700 nm of at least 2:1.-   20. The article of clause 19, wherein the retroreflective substrate    comprises at least one of a tape, a sign, a vehicle, a marker, and    clothing.-   21. A coating composition for application over a retroreflective    substrate, comprising:    -   a resin; and    -   a pigment suitable to absorb and/or scatter electromagnetic        radiation in a wavelength range of 800 nm to 2000 nm;    -   wherein a coating formed from the coating composition comprises        a ratio of electromagnetic radiation extinction at a wavelength        of 905 nm and/or 1550 nm to electromagnetic radiation extinction        averaged over a wavelength range of 400 nm to 700 nm of at least        2:1.-   22. The coating composition of clause 21, wherein the coating    comprises a ratio of electromagnetic radiation extinction at a    wavelength of 905 nm and/or 1550 nm to electromagnetic radiation    extinction averaged over a wavelength range of 400 nm to 700 nm of    at least 4:1.-   23. The coating composition of any one of clauses 21-22, wherein the    coating comprises a ratio of electromagnetic radiation absorption at    a wavelength of 905 nm and/or 1550 nm to electromagnetic radiation    absorption averaged over a wavelength range of 400 nm to 700 nm of    at least 2:1.-   24. The coating composition of any one of clauses 21-23, wherein the    coating comprises a ratio of electromagnetic radiation absorption at    a wavelength of 905 nm and/or 1550 nm to electromagnetic radiation    absorption averaged over a wavelength range of 400 nm to 700 nm of    at least 4:1.-   25. The coating composition of any one of clauses 21-24, wherein the    coating comprises a ratio of electromagnetic radiation scattering at    a wavelength of 905 nm and/or 1550 nm to electromagnetic radiation    extinction averaged over a wavelength range of 400 nm to 700 nm of    at least 2:1.-   26. The coating composition of any one of clauses 21-25, wherein the    pigment comprises at least one of zinc oxide, alumina, antimony tin    oxide, tungsten oxide, gold nanoparticles, silver nanoparticles,    copper nanoparticles, lanthanum hexaboride, dicopper hydroxide    phosphate, and a phthalocyanine.-   27. The coating composition of any one of clauses 21-26, wherein the    pigment comprises lanthanum hexaboride.-   28. The coating composition of any one of clauses 21-27, wherein the    pigment comprises an average particle size of 1 nm to 5000 nm.-   29. The coating composition of any one of clauses 21-28, wherein the    pigment comprises an average particle size of 10 nm to 150 nm.-   30. The coating composition of any one of clauses 21-29, wherein the    coating absorbs at least 0.1 absorbance units of electromagnetic    radiation at a wavelength of 905 nm.-   31. The coating composition of any one of clauses 21-30, wherein the    coating absorbs at least 0.2 absorbance units of electromagnetic    radiation at a wavelength of 1550 nm.-   32. A system comprising:    -   the coating composition of any one of clauses 21-31 disposed        over a retroreflective substrate, wherein the system comprises a        CIELAB color difference, ΔE, of 25 or less when compared to the        retroreflective substrate without the coating, as measured using        an integrating sphere with D65 Illumination, 10° observer with        specular component included.-   33. The system of clause 32, wherein the retroreflective substrate    comprises at least one of a tape, a sign, a vehicle, a marker, and    clothing.-   34. The coating composition of any one of clauses 21-31 and/or the    system of any one of clauses 32-33, wherein the resin comprises at    least one of a thermosetting film-forming resin and a thermoplastic    film-forming resin.-   35. The coating composition of any one of clauses 21-31 and 34    and/or the system of any one of clauses 32-33, wherein the resin    further comprises at least one of acrylic polymers, polyester    polymers, polyurethane polymers, polyamide polymers, polyether    polymers, polysiloxane polymers, copolymers thereof, and mixtures    thereof.-   36. The coating composition of clauses 21-31 and 34-35 and/or the    system of any one of clauses 32-33, wherein the coating transmits 80    percent or less of electromagnetic radiation at a wavelength of 905    nm.-   37. A method for producing a retroreflective article with increased    electromagnetic radiation extinction at a wavelength of 905 nm    and/or 1550 nm, the method comprising:    -   depositing a coating composition over a retroreflective        substrate to form a coating, the coating composition comprising:        -   a resin; and        -   a pigment suitable to absorb and/or scatter electromagnetic            radiation in a wavelength range of 800 nm to 2000 nm;        -   wherein the coating comprises a ratio of electromagnetic            radiation extinction at a wavelength of 905 nm and/or 1550            nm to electromagnetic radiation extinction averaged over a            wavelength range of 400 nm to 700 nm of at least 2:1.-   38. A retroreflective article comprising:    -   a retroreflective substrate; and    -   a coating disposed over the retroreflective substrate, the        coating comprising:        -   a resin; and        -   a pigment suitable to absorb and/or scatter electromagnetic            radiation in a wavelength range of 800 nm to 2000 nm;        -   wherein the coating comprises a ratio of electromagnetic            radiation extinction at a wavelength of 905 nm and/or 1550            nm to electromagnetic radiation extinction averaged over a            wavelength range of 400 nm to 700 nm of at least 2:1.-   39. The article of clause 38, wherein the retroreflective substrate    comprises at least one of a tape, a sign, a vehicle, a marker, and    clothing.

Various features and characteristics are described in this specificationto provide an understanding of the composition, structure, production,function, and/or operation of the invention, which includes thedisclosed compositions, coatings, and methods. It is understood that thevarious features and characteristics of the invention described in thisspecification can be combined in any suitable manner, regardless ofwhether such features and characteristics are expressly described incombination in this specification. The Inventors and the Applicantexpressly intend such combinations of features and characteristics to beincluded within the scope of the invention described in thisspecification. As such, the claims can be amended to recite, in anycombination, any features and characteristics expressly or inherentlydescribed in, or otherwise expressly or inherently supported by, thisspecification. Furthermore, the Applicant reserves the right to amendthe claims to affirmatively disclaim features and characteristics thatmay be present in the prior art, even if those features andcharacteristics are not expressly described in this specification.Therefore, any such amendments will not add new matter to thespecification or claims and will comply with the written description,sufficiency of description, and added matter requirements.

Any numerical range recited in this specification describes allsub-ranges of the same numerical precision (i.e., having the same numberof specified digits) subsumed within the recited range. For example, arecited range of “1.0 to 10.0” describes all sub-ranges between (andincluding) the recited minimum value of 1.0 and the recited maximumvalue of 10.0, such as, for example, “2.4 to 7.6,” even if the range of“2.4 to 7.6” is not expressly recited in the text of the specification.Accordingly, the Applicant reserves the right to amend thisspecification, including the claims, to expressly recite any sub-rangeof the same numerical precision subsumed within the ranges expresslyrecited in this specification. All such ranges are inherently describedin this specification such that amending to expressly recite any suchsub-ranges will comply with the written description, sufficiency ofdescription, and added matter requirements.

Also, unless expressly specified or otherwise required by context, allnumerical parameters described in this specification (such as thoseexpressing values, ranges, amounts, percentages, and the like) may beread as if prefaced by the word “about,” even if the word “about” doesnot expressly appear before a number. Additionally, numerical parametersdescribed in this specification should be construed in light of thenumber of reported significant digits, numerical precision, and byapplying ordinary rounding techniques. It is also understood thatnumerical parameters described in this specification will necessarilypossess the inherent variability characteristic of the underlyingmeasurement techniques used to determine the numerical value of theparameters.

Notwithstanding that numerical ranges and parameters setting forth thebroad scope of the invention are approximations, numerical values areset forth in the specific examples are reported precisely as possible.Any numerical value, however, inherently contains certain errorsnecessarily resulting from the standard variation found in theirrespective testing measurements.

The invention(s) described in this specification can comprise, consistof, or consist essentially of the various features and characteristicsdescribed in this specification. The terms “comprise” (and any form ofcomprise, such as “comprises” and “comprising”), “have” (and any form ofhave, such as “has” and “having”), “include” (and any form of include,such as “includes” and “including”), and “contain” (and any form ofcontain, such as “contains” and “containing”) are open-ended linkingverbs. Thus, a composition, coating, or method that “comprises,” “has,”“includes,” or “contains” one or more features and/or characteristicspossesses those one or more features and/or characteristics but is notlimited to possessing only those one or more features and/orcharacteristics. Likewise, an element of a composition, coating, orprocess that “comprises,” “has,” “includes,” or “contains” one or morefeatures and/or characteristics possesses those one or more featuresand/or characteristics but is not limited to possessing only those oneor more features and/or characteristics and may possess additionalfeatures and/or characteristics.

The grammatical articles “a,” “an,” and “the,” as used in thisspecification, including the claims, are intended to include “at leastone” or “one or more” unless otherwise indicated. Thus, the articles areused in this specification to refer to one or more than one (i.e., to“at least one”) of the grammatical objects of the article. By way ofexample, “a component” means one or more components, and thus, possiblymore than one component is contemplated and can be employed or used inan implementation of the described compositions, coatings, andprocesses. Nevertheless, it is understood that use of the terms “atleast one” or “one or more” in some instances, but not others, will notresult in any interpretation where failure to use the terms limitsobjects of the grammatical articles “a,” “an,” and “the” to just one.Further, the use of a singular noun includes the plural, and the use ofa plural noun includes the singular, unless the context of the usagerequires otherwise.

Any patent, publication, or other document identified in thisspecification is incorporated by reference into this specification inits entirety unless otherwise indicated but only to the extent that theincorporated material does not conflict with existing descriptions,definitions, statements, illustrations, or other disclosure materialexpressly set forth in this specification. As such, and to the extentnecessary, the express disclosure as set forth in this specificationsupersedes any conflicting material incorporated by reference. Anymaterial, or portion thereof, that is incorporated by reference intothis specification, but which conflicts with existing definitions,statements, or other disclosure material set forth herein, is onlyincorporated to the extent that no conflict arises between thatincorporated material and the existing disclosure material. Applicantreserves the right to amend this specification to expressly recite anysubject matter, or portion thereof, incorporated by reference. Theamendment of this specification to add such incorporated subject matterwill comply with the written description, sufficiency of description,and added matter requirements.

Whereas particular examples of this invention have been described abovefor purposes of illustration, it will be evident to those skilled in theart that numerous variations of the details of the present invention maybe made without departing from the invention as defined in the appendedclaims.

While the present disclosure provides descriptions of various specificaspects for the purpose of illustrating various aspects of the presentdisclosure and/or its potential applications, it is understood thatvariations and modifications will occur to those skilled in the art.Accordingly, the invention or inventions described herein should beunderstood to be at least as broad as they are claimed and not as morenarrowly defined by particular illustrative aspects provided herein.

What is claimed is:
 1. A coating composition for application over aretroreflective substrate, comprising: a resin; and a pigment suitableto absorb and/or scatter electromagnetic radiation in a wavelength rangeof 800 nm to 2000 nm; wherein a coating formed from the coatingcomposition comprises a ratio of reduction in electromagnetic radiationretroreflectance at a wavelength of 905 nm and/or 1550 nm to reductionin electromagnetic radiation retroreflectance averaged over a wavelengthrange of 400 nm to 700 nm of at least 2:1.
 2. The coating composition ofclaim 1, wherein the coating comprises a ratio of reduction inelectromagnetic radiation retroreflectance at a wavelength of 905 nmand/or 1550 nm to reduction in electromagnetic radiationretroreflectance averaged over a wavelength range of 400 nm to 700 nm ofat least 4:1.
 3. The coating composition of claim 1, wherein the coatingcomprises a ratio of electromagnetic radiation extinction at awavelength of 905 nm and/or 1550 nm to electromagnetic radiationextinction averaged over a wavelength range of 400 nm to 700 nm of atleast 2:1.
 4. The coating composition of claim 1, wherein the coatingcomprises a ratio of electromagnetic radiation extinction at awavelength of 905 nm and/or 1550 nm to electromagnetic radiationextinction averaged over a wavelength range of 400 nm to 700 nm of atleast 4:1.
 5. The coating composition of claim 1, wherein the coatingcomprises a ratio of electromagnetic radiation absorption at awavelength of 905 nm and/or 1550 nm to electromagnetic radiationabsorption averaged over a wavelength range of 400 nm to 700 nm of atleast 2:1.
 6. The coating composition of claim 1, wherein the coatingcomprises a ratio of electromagnetic radiation scattering at awavelength of 905 nm and/or 1550 nm to electromagnetic radiationscattering averaged over a wavelength range of 400 nm to 700 nm of atleast 2:1.
 7. The coating composition of claim 1, wherein the pigmentcomprises at least one of zinc oxide, alumina, antimony tin oxide,tungsten oxide, gold nanoparticles, silver nanoparticles, coppernanoparticles, lanthanum hexaboride, dicopper hydroxide phosphate, and aphthalocyanine.
 8. The coating composition of claim 1, wherein thepigment comprises lanthanum hexaboride.
 9. The coating composition ofclaim 1, wherein the pigment comprises an average particle size of 1 nmto 5000 nm.
 10. The coating composition of claim 1, wherein the pigmentcomprises an average particle size of 10 nm to 150 nm.
 11. The coatingcomposition of claim 1, wherein the coating absorbs at least 0.1absorbance units of electromagnetic radiation at a wavelength of 905 nm.12. The coating composition of claim 1, wherein the coating absorbs atleast 0.2 absorbance units of electromagnetic radiation at a wavelengthof 1550 nm.
 13. A system comprising: the coating composition of claim 1disposed over a retroreflective substrate, wherein the system comprisesa CIELAB color difference, ΔE, of 25 or less when compared to theretroreflective substrate without the coating, as measured using anintegrating sphere with D65 Illumination, 10° observer with specularcomponent included.
 14. The system of claim 13, wherein theretroreflective substrate comprises at least one of a tape, a sign, avehicle, a marker, and clothing.
 15. The coating composition of claim 1,wherein the resin comprises at least one of a thermosetting film-formingresin and a thermoplastic film-forming resin.
 16. The coatingcomposition of claim 1, wherein the resin further comprises at least oneof acrylic polymers, polyester polymers, polyurethane polymers,polyamide polymers, polyether polymers, polysiloxane polymers,copolymers thereof, and mixtures thereof.
 17. The coating composition ofclaim 1, wherein the coating transmits 80 percent or less ofelectromagnetic radiation at a wavelength of 905 nm.
 18. A method forproducing a retroreflective article with reduced electromagneticradiation retroreflection at a wavelength of 905 nm and/or 1550 nm, themethod comprising: depositing a coating composition over aretroreflective substrate to form a coating, the coating compositioncomprising: a resin; and a pigment suitable to absorb and/or scatterelectromagnetic radiation in a wavelength range of 800 nm to 2000 nm;wherein the coating comprises a ratio of reduction in electromagneticradiation retroreflectance at a wavelength of 905 nm and/or 1550 nm toreduction in electromagnetic radiation retroreflectance averaged over awavelength range of 400 nm to 700 nm of at least 2:1.
 19. Aretroreflective article comprising: a retroreflective substrate; and acoating disposed over the retroreflective substrate, the coatingcomprising: a resin; and a pigment suitable to absorb and/or scatterelectromagnetic radiation in a wavelength range of 800 nm to 2000 nm;wherein the coating comprises a ratio of reduction in electromagneticradiation retroreflectance at a wavelength of 905 nm and/or 1550 nm toreduction in electromagnetic radiation retroreflectance averaged over awavelength range of 400 nm to 700 nm of at least 2:1.
 20. The article ofclaim 19, wherein the retroreflective substrate comprises at least oneof a tape, a sign, a vehicle, a marker, and clothing.